The present application claims priority under 35 U.S.C. 119 of Japanese Patent Application No. 2002-9443 filed on Jan. 18, 2002, the entire contents thereof being hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a method for adjusting an assembly jig that includes a jig frame, a workpiece support provided in the jig frame for supporting a workpiece, and an actuator for moving the workpiece support relative to the jig frame.
2. Description of Background Art
In order to indicate the positions of rivet holes, bend lines, trim lines, etc. on a workpiece such as a skin panel of an aircraft, it is necessary for the workpiece to be positioned accurately and mounted rigidly on an assembly jig. The assembly jig is designed so that the workpiece is supported by a plurality of workpiece supports provided in a jig frame, but since the workpiece supports have a rigidity lower than the jig frame having a high rigidity, the positional relationship of the workpiece supports relative to the jig frame is slightly misaligned due to the influence of aging and changes in temperature. As a result, the positional relationship of the workpiece relative to the jig frame is also slightly misaligned.
The thus-caused misalignment is conventionally corrected by periodically measuring the positional relationship of the workpiece supports relative to the jig frame and placing a shim or a spacer on a part where the workpiece supports are fixed to the jig frame.
When the positions of the workpiece supports relative to the jig frame are adjusted using a shim or a spacer, the operation is complicated, and not only does it require much time and labor, but there is also a limit to the precision of the adjustment, which is a problem.
The present invention has been carried out in view of such circumstances, and it is an object thereof to easily and accurately correct the deteriorated precision of an assembly jig caused by the influence of aging and thermal expansion.
In order to achieve the object of the invention, in accordance with the present invention, there is proposed a method for adjusting an assembly jig comprising a jig frame, a workpiece support provided in the jig frame for supporting a workpiece, and an actuator for moving the workpiece support relative to the jig frame, the method comprising: operating a position measurement device to determine the coordinates of fixed reference points of the jig frame; establishing preset coordinates of a measurement reference point of the workpiece support relative to the fixed reference points; operating the position measurement device to determine the measured coordinates of the measurement reference point relative to the fixed reference points; determining the deviation of the measured coordinates of the measurement reference point from the preset coordinates of the measurement reference point; and operating the actuator, as needed, to adjust the position of the workpiece support so that the deviation of the measured coordinates of the measurement reference point from the preset coordinates of the measurement reference point is no greater than a predetermined value.
With this method, the positional coordinates of the measurement reference point of the workpiece support relative to the coordinate system fixed to the jig frame are preset; the positions of the coordinate reference points of the jig frame and the position of the measurement reference point of the workpiece support are then measured by means of the position measurement device; the positional coordinates of the measurement reference point of the workpiece support relative to the coordinate system fixed to the jig frame are then calculated based on the measurement results obtained by the position measurement device; the deviation of the calculated positional coordinates from the preset positional coordinates of the workpiece support is calculated; and the actuator is operated so as to make the deviation the predetermined value or less. Therefore, even when the position of the workpiece support relative to the jig frame is misaligned due to aging or changes in temperature, the misalignment can be automatically corrected so as to make the positional coordinates of the measurement reference point of the workpiece support closer to the preset positional coordinates. As a result, it is unnecessary to carry out a complicated adjustment operation using a shim or a spacer each time the misalignment of the workpiece support occurs, and moreover the accuracy of the adjustment can be greatly enhanced in comparison with a manual operation.
The object of the invention is also realized by a method for adjusting an assembly jig comprising a jig frame, a plurality of workpiece supports provided in the jig frame for supporting a workpiece, and a separate actuator for moving each workpiece support relative to the jig frame, the method comprising: operating a position measurement device to determine the coordinates of fixed reference points of the jig frame; establishing preset coordinates of a measurement reference point of each workpiece support relative to the fixed reference points; operating the position measurement device to determine the measured coordinates of each measurement reference point relative to the fixed reference points; determining the deviation of the measured coordinates of each measurement reference point from the preset coordinates of the measurement reference point; and operating the actuator, as needed, to adjust the position of each workpiece support so that the deviation of the measured coordinates of each measurement reference point from the preset coordinates of the measurement reference point is no greater than a predetermined value.
The object of the invention is also realized by a system for positioning a workpiece, the system comprising: a jig frame; a workpiece support provided in the jig frame for supporting a workpiece; an actuator for moving the workpiece support relative to the jig frame; a position measurement device for determining (1) the coordinates of fixed reference points of the jig frame and (2) the measured coordinates of a measurement reference point of the workpiece support relative to the fixed reference points; means for establishing preset coordinates of the measurement reference point relative to the fixed reference points; means for determining the deviation of the measured coordinates of the measurement reference point from the preset coordinates of the measurement reference point; and means for operating the actuator, as needed, to adjust the position of the workpiece support so that the deviation of the measured coordinates of the measurement reference point from the preset coordinates of the measurement reference point is no greater than a predetermined value.
In an embodiment of the invention, tooling balls are used to mark the coordinate reference points of the jig frame, and a tooling ball is used to mark the measurement reference point of the workpiece support.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.